Biological significance of non-acetylated metallothionein

The biological significance of non-acetylated metallothionein (MT) was inve stigated from the viewpoint of N-alpha-acetylation after induction of MT sy nthesis by metallic and non-metallic inducers, by partial hepatectomy and u nder physiological conditions. N-alpha-Acetylated and non-acetylated forms of MT-2 in liver supernatants and plasma were detected by the tandem size-e xclusion and anion-exchange HPLC columns with in-line detection by mass spe ctrometry. The non-acetylated isoform of MT-2 (MT-2') was present at a comp arable level to the N-alpha-acetylated form of MT-2 (MT-2) at an early stag e after induction by not only zinc but also cadmium, and by partial hepatec tomy in the: livers of rats. Plasma MT-2 in neonatal rats was similar to li ver MT-2 in the composition of N-alpha-acetylated and non-acetylated forms, suggesting that there are no differences in the roles of N-alpha-acetylati on of MT in the extracellular trafficking of MT. The column switching HPLC method with in-line detection by inductively coupled argon plasma mass spec trometry; (ICP-MS) was shown to be a sensitive and powerful method to detec t MT proteins at not only isoform level but also at acetylated and non-acet ylated form levels. (C) 1999 Elsevier Science B.V. All rights reserved.